Thursday, 30 April 2009

People with limb paralysis caused by a recent stroke or brain injury often deny that they have a problem - a condition known as "anosognosia". As well as being a neurological curiosity, anosognosia has serious practical implications. Such patients often won't cooperate in rehabilitation exercises or will deny they need certain medications. Now Aikaterini Fotopoulou and colleagues think they may have stumbled on a way to ameliorate the condition.

The intervention involves the patient watching a video of themselves attempting to perform a given movement instruction. Fotopoulou's team tested this on a 67-year-old women who for 22 days since her stroke had displayed anosognosia for her left-sided paralysis. For example, when asked to reach the doctor's hand with her left hand, she would consistently use her right hand. She knew it was her right hand but couldn't or wouldn't explain why she hadn't reached with her left.

By contrast, when the woman was shown a 90 second video clip of herself performing these tests, she showed sudden and immediate insight into her condition. "I cannot move at all," she said. Asked what made her change her mind, she said: "The video. I did not realise I looked like this." Anosognosic symptoms do usually fade with time, but not in an abrupt fashion like this.

The researchers explained that different regions in the brain support a first-person and third-person recognition of ourselves and it's possible that the areas supporting a third-person perspective were spared in this woman (and likely will be in many other people with anosognosia too), thus allowing her to appreciate the reality of her condition on the video.

Another explanation for the finding is that there may be a difference between a patient's insight during an attempted movement and their insight when watching themselves retrospectively.

This would be consistent with another recent study by Fotopoulou's group, in which patients with anosognosia had to judge whether a prosthetic hand, made to look like their own, had moved or not. The patients, but not controls, were more likely to erroneously report the hand had moved if they'd simultaneously been planning a movement of their own. In other words, the patient's intention to move seemed to override the visual feedback showing that no movement had occurred. In the current study, the patient may have understood events when watching the video because she wasn't engaged in any concurrent attempt to move.
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